Plainville, IL has a population of 334 and is the 21,883rd largest city in the United States. The population density is 1,453 per sq mi which is 554% higher than the Illinois average and 1504% higher than the national average. The median age in Plainville is 33 which is approximately 12% lower than the Illinois average of 37. In Plainville, 54% of the population over 15 years of age are married, 94% speak English and 1% speak Spanish. 73% of Plainville residents were born in Illinois, 25% were born out of state, 0% were born outside of the United States and 2% were foreign born.